With the engine in the car, CAM removal for any '60s benz straight-6 is as follows:
1. Remove cylinder head.
2. Cam is now off.
Not fun, but that's how it has to be done. The cam pedistals are held on with head bolts. Too many of them have to be removed to get the towers off. You CAN remove the cams on the v8s because of the difference in bolt patterns.
With the engine out of the car, the cam can be slipped off backwards; which would be through the firewall and into the passenger with it in the car.
Contact Elgin cams (they have a website I think) for regrind info. They have lots of vintage MB experience.
However, I don't anybody that has reground a benz cam, just to get more out of a suggish engine. If a benz engine is being a dog, it's either because it IS a dog, or it is in need of major overhaul. Is your compression OK? Did you use copper or platinum plug? Perhaps your fuel delivery system is in major need of help? What about your ignition system?
There are three versions of that engine, the "standard", "low compression" and "USA spec". Knowing your engine number 127.xxx can identify it.